The present invention relates generally to optical fibers. More specifically, the present invention pertains to methods of aligning optical fibers. The present invention is particularly, though not exclusively, useful for aligning optical fibers in a fixed array and locating those optical fibers with a high degree of precision.
In optical systems having more than one optical fiber, it is often challenging to properly arrange the various optical fibers, and secure them in place. This challenge is further compounded in systems where the precise location of the core of each optical fiber must be known.
One such system is an optical cross connect switch. In an optical cross connect switch, it is necessary to precisely position both an input optical fiber and an output optical fiber in order for the fibers to transmit light efficiently between them. Because the diameter of the core of a typical optical fiber is five to ten microns (5-10 xcexcm) it is necessary to position the ends of the optical fiber very precisely. In fact, it is advantageous to position the ends of the optical fiber such that the position of the core of the fiber is known to within one (1) or two (2) microns.
Accordingly, it is an object of the present invention to provide an apparatus and method for aligning optical fibers in a fixed array where the core of the optical fiber is located with a high degree of precision.
The present invention provides for the manufacture of large arrays of optical fibers with a high degree of precision in the placement of the fibers, typically to within five (5) microns, or one-half of the diameter of the core of the typical fiber. This precision is adequate to enable a control system to acquire the position of the end of an optical fiber without the incorporation of a random, or regional, search for the position of the fiber.
The method of the present invention for creating an array of optical fibers includes at least three (3) steps. The first step includes arranging a number of glass ferrules into a two-dimensional array. Each ferrule is formed with a longitudinal bore sized to closely receive an optical fiber. The outside diameters of the ferules are very precise, and thus, the ferules may be placed in contact with one another to create a very precise two-dimensional ferrule array. These ferrules may be fixed together with an ultraviolet curing epoxy, for example, to provide a rigid array of ferrules, and to minimize any movement of the ferrules during the curing process.
Once the ferrules are arranged in a two-dimensional array and secured in place in the first step, step two begins with the optical fibers being inserted through the ferrules until the ends extend approximately five to ten millimeters (5-10 mm) from the end of the ferrules. The fibers are then fixed in position within the ferrules with ultraviolet curing epoxy, for example, or any other similar means for securing the optical fibers in place within the ferrule.
Once the optical fibers are properly positioned and secured in the ferrule array, a substrate formed with a corresponding array of precision fiber alignment holes is brought near the fiber array such that each optical fiber will extend at least partially into a fiber alignment hole. Each fiber alignment hole may be formed with at least one corner with a known location. Once positioned over the optical fibers, the substrate is then displaced, or offset, slightly in one or more directions to assure that the end portion of the optical fibers make contact with the inside edge of the alignment hole, preferably in the location of the corner. Because the alignment holes and specifically, the corner of each alignment hole, may be very precisely formed in the substrate, the location of the end of the optical fiber may be very precisely determined. The substrate and the fiber array may be fixed together using a bonding block and epoxy, for example, thereby maintaining their offset position and completing the assembly.
The resulting assembly provides for an easily manufacturable two-dimensional array of optical fibers where the precise location of the end of each optical fiber is controlled. In fact, because the corners of the alignment holes formed in the substrate may be very precisely located, the location of the core of each optical fiber is also precisely determined within the assembly to within a few microns.